The present invention concerns a gas turbine engine such as a turbo jet engine for an aircraft, of the type including a compressor and an expansion turbine of which the respective rotors are axially spaced one from the other along the longitudinal axis of the engine and which are joined, both in rotation and in axial traction by a main coupling device.
In the case of a twin spool turbo jet engine (that is to say, a low pressure spool and a high pressure section rotating independently one from the other), the invention has application to the low pressure spool comprising the low pressure compressor rotor (or fan) disposed at the inlet side, and a low pressure turbine disposed at the exit end of the jet engine.
An incident rather rare, but dreaded in aviation, consists of the ingestion in flight of a bird by the turboreactor.
This incident can provoke damages all the more serious when the ingested bird is voluminous and heavy, for example, weighing more than a few pounds. The impact of the bird can, in fact, cause the rupture at the base of a plurality of blades of the first stage of the low pressure compressor (or fan), of such a nature that the pieces of the blades can become lodged between the rotor and the stator of this compressor and thus cause braking of the said rotor.
The result is that in the main coupling device between the rotors of this compressor and the expansion turbine associated with the latter, a brutal shearing force which, on account of active power of the said turbine, can proceed until the torsional resistance of the device is exceeded and can lead in consequence, to its rupture.
This rupture of the coupling device can, in turn, cause the ejection of the compressor rotor or the fan towards the front, and the ejection of the rotor of the corresponding turbine, towards the rear. One must bear in mind, on this subject, that during operation of the compressor and turbine, the rotors are subject to axial forces directed respectively towards the front and towards the rear, and this is the reason for which the main coupling device must be made able to resist axial traction force.
Now such an ejection of the compressor and turbine rotors is particularly dangerous and can proceed to the point of causing total loss of the aircraft.